1. Field of the Invention
The present invention relates to a liquid crystal display device, and more particularly to a liquid crystal display device that is adapted for displaying a detailed expression of an image, and a driving method thereof.
2. Discussion of the Related Art
A liquid crystal display device controls the light transmissivity of liquid crystal cells in accordance with a video signal to display a picture. An active matrix type of liquid crystal display device is advantageous in displaying a motion picture because such a device utilizes active control of switching devices. A thin film transistor is mainly used as the switching device in the active matrix type of liquid crystal display device.
Recently, application of liquid crystal display devices has expanded from being used as monitors and display devices in office equipment to televisions. Accordingly, manufacturers of liquid crystal display devices have been investing heavily in improving picture quality to compete with existing cathode ray tubes (CRTs). As part of increasing picture quality, various methods of improving contrast ratio and brightness have been proposed.
FIG. 1 represents a related art data stretching device. As shown in FIG. 1, the data stretching device includes a histogram analysis part 12 (i.e., an on-screen-display (OSD) input part), a stretching curve selection part 11, and N number of data stretching curves 13(1) to 13(N). The histogram analysis part 12 calculates the histogram of an input digital video data RGB(IN), i.e., the frequency distribution function by gray levels. The histogram analysis part 12 supplies an OSD stretching selection command inputted from a user and/or a calculated histogram result to the stretching curve selection part 11. The stretching curve selection part 11 selects any one of the N number of data stretching curves 13(1) to 13(N) in accordance with the OSD stretching selection command or the histogram result from the histogram analysis part 12.
Pre-set stretching curves different from each other are stored as the data stretching curves 13(1) to 13(N). Any one of the curves 13(1) to 13(N) is selected by the stretching curve selection part 11. The data RGB(IN) is modulated by a selected one of a stretching curve 13(1) to 13(N) by the stretching curve selection part 11. The data stretching curves 13(1) to 13(N) are each made up of a lookup table stored in memory 13 and use the RGB(IN) data from the stretching curve selection part 11 as an address to output a stretching data corresponding to the RGB(IN) data. However, in the related art data stretching device, picture quality may worsen in accordance with the image, and the ability to express the gray levels in detail is difficult.